Tuning dial for radio receiving sets



March 29, 1938. v

J, H. CLARK ET AL TUNING DIAL FOR RADIO RECEIVING SETS Filed Sept. 27, 1937 2 Sheets-Sheet l March 29, 1938. J. H. CLARK E'T AL 2,112,734

TUNING DIAL FOR RADIO RECEIVING SETS Filed Sept. 27, 1937 2 Sheets-Sheet 2 Patented Mar. 29, 1938 PATENT OFFICE TUNING DIAL FOR RAD-I RECEIVING SETS Jesse H. Clark, Chicago, and John Kelly Johnson, Evanston, Ill., assignors to Wells-Gardner & Company, Chicago, 111., a corporation of Illinois Application September 27, 1937, Serial No. 165,866

Claims.

This invention is concerned with a tuning dial of the screen type onto which may be projected the image of a selected scale. Such a dial is peculiarly suited for radio receiving sets. The

5 means for operating the present dial is interconnected also withan associated tuning condenser so as to assure coordinated action therebetween.

For its principal objects our invention is directed to certain features of improvement by which a simple and inexpensive mechanism is utilized for projecting images a relatively short distance within a space which is shielded only partially from external light, natural or otherwise; by which an optical system is mounted to swing about an axis which is substantially coincident with the focal point thereof so that the light rays may pass through a selected scale or special area of the slide; and by which a rugged construction is produced capable of operating de- 20 pendably with little or no attention over a long period of time. A mechanism which embodies such features of improvement is illustrated in the accompanying drawings in the manner following:

Figure 1 is a plan View of a radio receiving chassis on which is mounted a projection type of tuning dial made according to this invention.

Fig. 2 is a vertical section through the chassis, taken on line 2-2 of Fig. 1, showing the projection apparatus in side elevation;

30 Fig. 3 is a vertical section, taken on line 3-3 of Fig. 1;

Fig. 4 is a detail in section, taken on line 4 of Fig. 2; and

Fig. 5 is a fragmentary view in elevation of the screen and its supporting plate.

The parts which are special to this invention may be mounted upon a chassis base A. As shown, they are assembled into a separate unit capable of being installed or removed independently of the remaining apparatus with which it is used. In this connection use is made of a vertical plate B in which is fixedly mounted a screen 0 (desirably of ground glass) on which is projected an image in the manner to be presently described. The screen, as shown, is provided with an opaque border 1 defining near each end a translucent elongated window 8.

Slidably mounted upon the rear side of the plate at each of its ends are elongated indicators v9 each having a marked portion l0 which is visible through the proximate screen window. A coil spring ll connects the plate and indicator in a manner to raise the latter to an upper position. Connected with one indicator is a flexible cord or wire I2 extending downwardly to a tone conment between the ears.

trol shaft d having an operating knob D, the position of the indicator being shifted with each actuation of the shaft to afford a visual engagement of the tone control adjustment at all times. i

The indicating mechanism at the opposite plate end is operable by a cord or flexible Wire l3 from a volume control shaft g having a suitable operating knob G. Connected with this latter shaft is the usual on-and-off switch (not shown).

Mounted with the aid of resilient cushions upon the chassis base is a supporting frame H With oppositely extending feet IS. The forward feet terminate in depending lugs l6 through which extend suitable fastenings which connect the screen plate immovably to the base. Joined to the supporting frame and extending rearwardly therefrom is a condenser frame I to the rear end of which is affixed a vertical post J with a bracket ll connecting its lower end to the chassis base. Supported upon the post is one end of a platform K which extends forwardly to be further supported by the frame H, and thence to the screen plate where it is formed with a depending flange I8 for convenient connection therewith as with screws 19. The structure just described, viz. the screen plate and frame elements rearwardly thereof is a rigid unit which is fixedly secured to the chassis base.

Extending rearwardly from the post J at spaced points near its top are two cars and 2| forming bearings for a spindle 22 whereon is secured a pulley 23 which is confined against axial move- Extending upwardly from the pulley on which it rests is a bushing 24 which is disposed axially Within a circular disk 25 forming the base of a cylindrical slide L. This disk is provided with upstanding marginal walls 26 defining an annular seat wherein is fitted the lower edge of a film 21 bent into circular form with its ends united. If desired, the top film edge may be turned down upon itself as at 28 to provide a reinforcement.

Rotary movements to the cylindrical slide are imparted by an endless belt transmission 30 which extends around the horizontal pulley 23 and thence forwardly over vertical pulleys 3|, and downwardly around one groove of a duplex pulley 32 which is mounted on the forward end of a condenser shaft 33 which extends horizontally through the frame J where it is journaled for rotation in upstanding plate bearings 34 and 35. Carried in the frame J are condenser plates, some fixed and others movable into and out of the spaces therebetween, the latter being mounted upon the shaft 33 so as to operate therewith.

As by a belt 36 which runs around the duplex pulley 32 and the control shaft f which is equipped with an operating knob F (see Fig. 1), adjusting movements may be imparted to the movable condenser plates concurrently with rotary movements on the part of the cylindrical slide.

The platform which extends between the slide and screen supports a pair of upstanding spaced plates 40 and 4| between" which is pivotally mounted a bracket M having forwardly and rearwardly depending arms 42 and 43, respectively. Between the supporting plates and the screen is an open-ended light box N of fiber or the like, secured to the platform as by a screw 44. To the bracket rear arm 43 is attached a vertically adjustable tube 45, open at top and bottom, adapted to support an illuminant 46 Which, as shown, is an electric light bulb which depends from an associated socket 41 whichis fitted adjustably into the upper end of the tube. The illuminated filament of the light bulb lies opposite a horizontal tube 48 through which light rays pass for projection through a condenser lens 49 which is fitted into the rear end of the tube 48, this lens forming part of a lens system which comprises also a compound projector lens of which one, the lens 50, is placed adjustably at the forward end of this tube. Adjacent the exterior of the cylindrical slide, and upstanding from the platform to which it is secured, is an apertured plate having a three-color screen 52 over its opening. The transparencies :r, y and 2 which form this screen are disposed horizontally edge to edge in such position that the light rays projected from the illuminant will pass through but one of them, depending upon the vertical adjust- 'ment of the pivoted bracket M. A second lens 55 of the compound projector, arranged forwardly of the color screen is carried by a sleeve 56 adjustably fitted into a. tube'51 which is formed in connection with the forwardly depending arm 42 of the bracket. By the means described, an optical system is provided for transmitting light rays from the illuminant through the several lenses, through the slide, color screen, and light box, and onto the screen where is projected an image that'is readily visible from the opposite or exterior side thereof.

The'pivoted mounting of the bracket M will now be explained. It is important that the light rays shall remain focused upon the screen in each of the adjusted positions of the bracket, consequently the center of pivotal movement should be approximately at the screen itself. In order to overcome certain mechanical difiiculties of such an arrangement, we provide in the bracket supporting plates 40 and 4| upper and lower opposed slots 60 and 6|, respectively, all of arcuate form with a common center which is coincident with a horizontal line extending through the focal point at the screen. Slidingly fitted within each pair of slots is a pin 62 carried in a bearing 63 which extends transversely of the bracket. Adjusting movements of the bracket about the focal point as a center are effected with the aid of a bell-crank mechanism (see Fig. 4) comprising a weight arm 65 underlying a rib 66 on the depending bracket arm 42 with a spring connection 6! to maintain the former in. engagement with the latter, the weight arm being extended from an offset bar 68 having at opposite ends ears 69 formed to receive a common pin ll] which is supported between lugs H which upstand from the platform K, a power arm 12 being depended from the forward ear for pivotal connection at 73 with a link 14 which joins at 15 with a crank arm 16 carried fast by the control shaft e having an operating knob E. As by a tail piece 11 which carries a friction button 18 adapted to engage within a selected socket 19 in a fixed plate 80, a detent is provided by which the shaft e with connected linkage, including the bracket M, is releasably secured in any of its adjusted positions of which three are indicated in the drawings.

By rotating the knob E a force is transmitted to the bell crank mechanism whereby the bracket M is rocked about the focal point as a center of movement, being either raised or lowered with a consequent change in the position of the entire optical system relative to the slide. Various scales may be marked upon the slide, each preferably extending circumferentially thereof so as to present different object areas from any selected one of which an image may be projected onto the screen, each such image being'differently colored by reason of the light rays being transmitted -through a separate color panel of the screen.

We claim: 7 e I 1. In a radio receiving set, a light projection dial comprising, in combination, a fixed image screen, a slide movable through a. single path, a plurality of lenses together with an illuminant forming an optical system, and a mounting for the optical system adapted for pivotal movement about an axis which substantially intersects the focal point of the light rays passing through the optical system.

2. In. a radio receiving set, a light projection dial comprising, in combination, a fixed image screen, a slide movable through a single path, and an optical system comprising a plurality of lenses and an illuminant, a common mounting for the lens system shiftable from one position. to another, and means guiding the mounting in its shifting movements in a manner whereby the focal point of the optical system will remain in a substantially fixed position with respect to the screen.

3. In a radio receiving set, a light projection dial comprising, in combination, a fixed image screen, a movable-slide, an optical system comprising lenses and an illuminant, anda pivotal mounting for the optical system located at a point remote from the screen adapted to guide the optical system through a swinging movement having a center substantially coincident with the screen; r

4. In a radio receiving set, a light projection dial comprising, in combination, a fixed image screen, an optical system comprising spaced lenses and an illuminant, a light box positioned intermediately of the screen and optical system, and a pivotal mounting for the optical system located adjacent the light box end which is remote from the screen adapted to confine movements of the optical system through a path whose center is substantially coincident with the screen. 5. In a radio receiving set, a light projection dial comprising, in combination, a fixed image screen, an optical system comprising spaced lenses and an illuminant, a circular rotatable slide enclosing the illuminant and one lens, and a pivotal mounting for the optical system permitting swinging movements thereof in a plane which is substantially coincident withthe slide axis about an axis which is substantially coincident with the 4 

